Molecular structure of alpha,beta-unsaturated ketones: 2-benzylidenecyclohexanone and some of its derivatives

The molecular structure of 2-benzylidenecyclohexanone is determined by X-ra y diffraction analysis. The data on molecular structures of alpha,beta-unsa turated ketones (including chiral 3R,6R-2-arylidene-3-methyl-6-isopropylcyc lohexanones) with the enone fragment fixed in the s-cis configuration by th e cyclohexane ring are considered. A characteristic feature of these molecu lar structures is the acoplanarity of the double bond with both the carbony l group and the benzene ring. The degree of acoplanarity depends on the nat ure of substituents in the arylidene and cyclohexanone fragments. The steri c stress of the studied molecular structures manifests itself in the presen ce of short intramolecular atomic contacts between the benzene ring and the cyclic >C(3)HR fragment (where R is hydrogen atom or substituent) and also in substantial distortions of bond angles at the sp(2) carbon atoms.